1. Field of the Invention
The present invention relates to an image forming apparatus and a paper feed control method for an image forming apparatus. More particularly, the present invention relates to an image forming apparatus capable of paper feed control while accurately detecting the weight of each sheet of paper stored in a paper storage part or the weight per unit number of sheets stored therein and further capable of judging, for example, whether or not the number of sheets remaining in the paper storage part is adequate for the designated number of copies to be made, and of displaying the result of the judgment. The present invention also relates to a paper feed control method for such an image forming apparatus.
2. Description of the Related Art
In the conventional image forming apparatus of the type described above, the detection of the remaining quantity of copying paper held in a paper storage part (paper feed cassette) cannot very accurately be performed. For example, the invention disclosed in Japanese Patent Application Unexamined Publication (KOKAI) No. Hei 10-148982 detects the amount of upward movement of the paper storage part by counting the number of motor pulses. On the other hand, the number of images formed is counted with a paper counting means to calculate the amount of upward movement per unit number of sheets of paper, and the number of remaining sheets is calculated from the amount of upward movement left.
The above-described conventional image forming apparatus uses the motor pulses to calculate the remaining quantity of paper. However, it is not easy to make the motor pulse accuracy correspond to the thickness of thin paper. The accuracy degrades particularly when sheets of paper different in thickness are used mixedly or when the reverse sides of used sheets are used, by way of example. When the accuracy of the calculation of the remaining quantity of paper is low, a problem may occur when the user leaves the place where the image forming apparatus is placed after setting and executing a copying operation for making a large number of copies. That is, when the user returns to the place, the desired copying operation may have undesirably been suspended because of a lack of paper.
The present invention was made to solve the above-described problems. Accordingly, an object of the present invention is to provide an image forming apparatus and a paper feed control method for an image forming apparatus capable of automatically performing the following operations: The number of copies made is counted, and every time a specific number of copies have been made, the weight of paper in the paper storage part is detected, whereby the weight per unit number of sheets of paper actually used can be accurately calculated from a specific decrease in the number of sheets in the paper storage part and a reduction in the weight. Thus, the number of sheets of paper remaining in the paper storage part can be accurately calculated on the basis of the result of the above calculation. Further, it is judged whether or not the number of remaining sheets of paper is adequate for the number of copies to be made. If the number of remaining sheets of paper is not adequate for the number of copies to be made, a warning is given.
To solve the above-described problems, the present invention provides an image forming apparatus having a paper storage part for storing sheets of paper for use in copying; a weight detecting part for detecting the weight of sheets of paper stored in the paper storage part; a paper feed counting part for counting sheets of paper fed for copying from the paper storage part; a checking sheet number setting part for setting a number of sheets for checking as a predetermined number of sheets of paper used to check a predetermined parameter concerning sheets of paper; and a weight calculating part for comparing the weights of sheets of paper detected by the weight detecting part before and after the paper feed counting part counts the number of sheets of paper fed equal to the number of sheets for checking to detect a decrease in weight of the sheets of paper, and for calculating the weight per sheet of paper or per unit number of sheets of paper on the basis of the decrease in weight and the number of sheets for checking.
Further, the image forming apparatus according to the present invention has a designating part for designating a number of copies to be made; a calculating part for calculating the number of remaining sheets of paper in the paper storage part on the basis of the weight per sheet of paper or per unit number of sheets of paper calculated by the weight calculating part and the weight of sheets of paper detected by the weight detecting part; and a judging part for judging whether or not the number of remaining sheets of paper calculated by the calculating part is adequate for the number of copies to be made designated by the designating part on the basis of the number of remaining sheets of paper and the number of copies to be made.
In this case, the image forming apparatus may have a warning display part for giving warning when the judging part judges that the number of remaining sheets of paper is not adequate for the number of copies to be made. The warning display part may include at least either a sound output unit for giving warning by sound or a control panel for displaying warning by an image.
Further, the image forming apparatus according to the present invention may have a memory part for storing the weight of standard paper, which is the weight per sheet of standard paper or per unit number of sheets of standard paper; and a calculating part for calculating the number of remaining sheets of paper stored in the paper storage part from the weight of sheets of paper detected by the weight detecting part and the weight of standard paper when the number of copies to be made is designated by the designating part at the time of starting. The number of sheets for checking set in the checking sheet number setting part may be changeable from the outside. Further, when the number of copies to be made designated by the designating part is smaller than the number of sheets for checking set in the checking sheet number setting part, the number of copies to be made can be set substitutionally in the checking sheet number setting part as the number of sheets for checking.
In the present invention, the weight detecting part comprises a weight sensor placed in the bottom of the paper storage part; a paper support plate supported by the weight sensor and loaded with paper; and a weight calculating part for reading the weight of the paper support plate that has previously been stored in memory and for subtracting the weight of the paper support plate from the weight of paper detected with the weight sensor to determine the weight of paper.
In addition, the present invention provides a paper feed control method for an image forming apparatus adapted to form an image on a sheet of paper fed from a paper storage part, wherein paper feed control is performed by carrying out steps including: a first paper weight detecting step of detecting the weight of sheets of paper stored in the paper storage part; a counting step of counting sheets of paper fed for copying from the paper storage part from a point of time at which weight detection is effected by the first paper weight detecting step; a second paper weight detecting step of detecting the weight of sheets of paper stored in the paper storage part when a predetermined number of sheets of paper fed has been counted by the counting step; and a weight calculating step of calculating the weight per sheet of the paper or per unit number of sheets of the paper on the basis of the weight of sheets of paper detected by the first paper weight detecting step and the weight of sheets of paper detected by the second paper weight detecting step, together with the predetermined number of sheets of paper.
In this case, the paper feed control method may include a remaining sheet number calculating step of calculating the number of remaining sheets of paper in the paper storage part on the basis of the weight per sheet of the paper or per unit number of sheets of the paper calculated by the weight calculating step and the weight of sheets of paper detected by the second paper weight detecting step.
Further, in this case, the paper feed control method may include a judging step of judging whether or not the calculated number of remaining sheets of paper is adequate for the designated number of copies to be made on the basis of the number of remaining sheets of paper and the designated number of copies to be made.
With the above-described arrangement, the number of copies made is counted, and every time a specific number of copies have been made, the weight of paper in the paper storage part is detected, whereby the weight per unit number of sheets of paper actually used can be accurately calculated from a specific decrease in the number of sheets in the paper storage part and a reduction in the weight. Thus, the number of sheets of paper remaining in the paper storage part can be accurately calculated on the basis of the result of the above calculation. Further, it is judged whether or not the number of remaining sheets of paper is adequate for the number of copies to be made. If the number of remaining sheets of paper is not adequate for the number of copies to be made, a warning is given. These operations can be performed automatically.